Lost Windows Install Key?

[Magic Jelly Bean Keyfinder] works with Windows 95, 98, ME, NT4, 2000, XP and Server 2003. Keyfinder also supports changing the key in an installed Windows 95, 98, ME or XP system. Magical Jelly Bean Keyfinder also is supposed to be able to display the CD keys for Office 97 and Office XP

This looks like another tool I need to store on my thumb drive before the holidays. I just have that feeling I will be working on someone's broken computer over Thanksgiving.